ABSTRACT
Title
Proapototic effect of tetradecylthioacetic acid (TTA) in anaplastic thyroid carcinoma cells (ARO): PPARs involvement.
Authors
G. Bianco, S. Marzocco, G. Autore
Department of Pharmaceutical and Biomedical Sciences, University of Salerno, Fisciano (SA), Italy
Department of Pharmaceutical and Biomedical Sciences, University of Salerno, Fisciano (SA), Italy
Abstract
Thia substituted fatty acids are saturated compounds which are modified by insertion of a sulfur atom at specific positions in the carbon backbone. During the last few years pleiotropic effects of the 3-thia fatty acid tetradecylthioacetic acid (TTA) have been revealed. TTA is a ligand for peroxisome proliferator-activated receptors (PPARs) (Bhurruth-Alcor et al., 2010) and promote hepatic proliferation of both mitochondria and peroxisomes and decrease serum triacylglycerol, cholesterol and free fatty acid levels in rats and dogs (Tronstad et al., 2001).
Because PPARs regulate the transcription of several genes involved in lipid metabolism and fat cell differentiation, they have been established as targets for the treatment of metabolic diseases over the past decade. However, PPARs agonists, used in diabetes treatment and dislipidemia, are reported to contribute in the regulation of differentiation, proliferation and apoptosis (Vanden Heuvel et al., 1999). Since PPARs are expressed by tumor and endothelial cells and PPAR ligands regulate cell growth, survival, migration, and invasion it has been investigated their role in the pathophysiology of tumorigenesis and angiogenesis (Roberts et al., 2002).
The aim of our study has been to investigate the antiproliferative effect of TTA, a PPARs activator, in papillary (NPA), follicular (FRO) and anaplastic (ARO) thyroid carcinoma cells, three different thyroid tumor cell types, focusing on its proapoptotic effect on undifferentiated anaplastic thyroid cells.
Citotoxic effect of TTA was evaluated by propidium iodide (PI) staining of hypodiploid nuclei and citofluorimetric analisys. TTA lead to time (24, 48 and 72 hours) and concentration (30-200µM) dependent apoptotic dead in NPA, FRO and particularly ARO thyroid carcinoma cells, which represent the most aggressive thyroid tumor cells type. Moreover cytofluorimetric analysis show that TTA cytotoxicity in ARO cells is not accompanied with alteration in cell cycle phases distribution. PPAR-α and PPAR-γ basal expression was evaluated in NPA, FRO and ARO cells by Western blot analysis and our results show that the ARO cells exhibited the highest expression in either receptors (P<0.001 and P<0.05 for PPAR-α and PPAR-γ respectively vs NPA and FRO cells). In ARO cells TTA in a concentration-dependent manner significantly reduced the expression of the antiapoptotic protein Bcl-2, induced cleavage and activation of poly(ADP-ribose) polymerase (PARP-1) and increased oxidative stress evaluated by thiobarbituric acid reactive substances (TBARS) assay. Interestingly after incubation of ARO cells with TTA and GW6471, antagonist for PPAR-α, or GW9662, PPAR-γ antagonist we observed a partially reversion of TTA mediated apoptosis only blocking PPAR-α. Moreover after TTA treatment ARO cells increase PPAR-α but not PPAR-γ in time dependent manner.
In conclusion our data showed that the TTA induced apoptosis in malignant anaplastic thyroid carcinoma cells and our results highlighted that its effect involved PPAR-α activation and oxidative stress increase.
References
Bhurruth-Alcor Y et al.,Bioorg Med Chem Lett, 2010, 20(3):1252-1255.
Roberts RA et al., Toxycology, 2002, 181:167-170.
Tronstad KJ al.,Biochem Pharmacol, 2001, 61(6):639-49.
Vanden Heuvel JP et al., J Nutr, 1999, 129:575-580.
Because PPARs regulate the transcription of several genes involved in lipid metabolism and fat cell differentiation, they have been established as targets for the treatment of metabolic diseases over the past decade. However, PPARs agonists, used in diabetes treatment and dislipidemia, are reported to contribute in the regulation of differentiation, proliferation and apoptosis (Vanden Heuvel et al., 1999). Since PPARs are expressed by tumor and endothelial cells and PPAR ligands regulate cell growth, survival, migration, and invasion it has been investigated their role in the pathophysiology of tumorigenesis and angiogenesis (Roberts et al., 2002).
The aim of our study has been to investigate the antiproliferative effect of TTA, a PPARs activator, in papillary (NPA), follicular (FRO) and anaplastic (ARO) thyroid carcinoma cells, three different thyroid tumor cell types, focusing on its proapoptotic effect on undifferentiated anaplastic thyroid cells.
Citotoxic effect of TTA was evaluated by propidium iodide (PI) staining of hypodiploid nuclei and citofluorimetric analisys. TTA lead to time (24, 48 and 72 hours) and concentration (30-200µM) dependent apoptotic dead in NPA, FRO and particularly ARO thyroid carcinoma cells, which represent the most aggressive thyroid tumor cells type. Moreover cytofluorimetric analysis show that TTA cytotoxicity in ARO cells is not accompanied with alteration in cell cycle phases distribution. PPAR-α and PPAR-γ basal expression was evaluated in NPA, FRO and ARO cells by Western blot analysis and our results show that the ARO cells exhibited the highest expression in either receptors (P<0.001 and P<0.05 for PPAR-α and PPAR-γ respectively vs NPA and FRO cells). In ARO cells TTA in a concentration-dependent manner significantly reduced the expression of the antiapoptotic protein Bcl-2, induced cleavage and activation of poly(ADP-ribose) polymerase (PARP-1) and increased oxidative stress evaluated by thiobarbituric acid reactive substances (TBARS) assay. Interestingly after incubation of ARO cells with TTA and GW6471, antagonist for PPAR-α, or GW9662, PPAR-γ antagonist we observed a partially reversion of TTA mediated apoptosis only blocking PPAR-α. Moreover after TTA treatment ARO cells increase PPAR-α but not PPAR-γ in time dependent manner.
In conclusion our data showed that the TTA induced apoptosis in malignant anaplastic thyroid carcinoma cells and our results highlighted that its effect involved PPAR-α activation and oxidative stress increase.
References
Bhurruth-Alcor Y et al.,Bioorg Med Chem Lett, 2010, 20(3):1252-1255.
Roberts RA et al., Toxycology, 2002, 181:167-170.
Tronstad KJ al.,Biochem Pharmacol, 2001, 61(6):639-49.
Vanden Heuvel JP et al., J Nutr, 1999, 129:575-580.